Twisted nematic micropolarizer and its method of manufacturing

ABSTRACT

The invention is a method for creating a micropolarizer, including providing a first plate having a first and a second surface, providing a second plate having a first and a second surface. Then coating a polyimide on each of the first surface of the two plates followed by rubbing the polyimide coated upon the first surface of the first plate along a predetermined direction and rubbing the polyimide coated upon the first surface of the second plate along a direction having a predetermined angle in relation to the predetermined direction. An alignment process includes aligning the first plate and the second plate having the first surface of the first plate and the first surface of the second plate facing each other thereby creating a space there between. In conclusion there is a filling of a liquid crystal material in the space whereby a cell, or film is created.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation-in-part of Non-provisionalapplication 10/045,871 ('871) filed Jan. 14, 2002 by Faris et al. and ishereby incorporated by reference.

BACKGROUND OF THE INVENTION

This disclosure is related to the development and the improvedmanufacturing of micropolarizers (μPol™) (micropol) based on twistednematic (TN) liquid crystals. VRex, Inc. and Reveo, Inc., the assigneeof this application and its parent have several patents and patentapplications with regard to the micropol. These prior art documentsdescribe several forms that the micropol may take (including alternatingrows, alternating columns and checkerboard configurations), varioussubstances that may be used to make them (polyvinyl alcohol, and varioustypes of liquid crystal), and various methods for fabrication. Many ofthese methods have shown great promise for manufacturing and are, infact, presently in use. These patents include U.S. Pat. No. 5,096,520('520) issued on Mar. 17, 1992 to Faris; U.S. Pat. No. 5,327,285 ('285)issued on Jul. 5, 1994 to Faris; U.S. Pat. No. 5,537,144 ('144) issuedJul. 16, 1996; U.S. Pat. No. 5,844,717 issued on Dec. 1, 1998; and U.S.Pat. No. 6,384,971 issued on May 7, 2002 to Faris.

Micropol (μPol) panels in which patterned polarizers having alternatelines of perpendicular polarization are used in conjunction withpolarizing glasses. In this technique, polyvinyl alcohol (PVA) λ/2retarder has been the base for building the μPol array. The fundamentalsof this μPol rely on the π phase shift induced by PVA. The μPol 100 isbuilt in such a way that it consists of alternately spaced lines with102 and without 104 the π phase shifter, as schematically shown in FIG.1.

The advantages of such a μPol include:

-   -   Simple processing;    -   Low cost;    -   High throughput;        The PVA based μPol, however, has its own shortcomings:    -   Poor spectral characteristics due to the phase shift mechanism;    -   Relatively thicker film thickness;    -   Relatively low spatial resolution;    -   Difficulty in line width control;    -   Poor thermal and humidity resistance.

There is room for improvement in developing new fabrication methods thatcan reduce the cost and the time involved in the manufacturing processitself and in the application of the micropol to flat panel LCD displaysor other flat rasterized display devices.

The purpose of this invention is to improve the processes of micropolfabrication and application, particularly for the TN-micropol describedin the '871 TN-micropol patent application

This invention describes alternative methods to manufacture a highquality μPol that will essentially eliminate all the above-mentionedproblems at a lower cost.

BRIEF SUMMARY OF THE INVENTION

The invention is a method for creating a micropolarizer, includingproviding a first plate having a first and a second surface, providing asecond plate having a first and a second surface. Then coating apolyimide on each of the first surface of the two plates followed byrubbing the polyimide coated upon the first surface of the first platealong a predetermined direction and rubbing the polyimide coated uponthe first surface of the second plate along a direction having apredetermined angle in relation to the predetermined direction. Analignment process includes aligning the first plate and the second platehaving the first surface of the first plate and the first surface of thesecond plate facing each other thereby creating a space there between.In conclusion there is a filling of a liquid crystal between the spaceswhereby a cell, or film is created.

The method for creating a micropolarizer includes providing a materialhaving a first and a second surface and then cleaning the material by2-propanol in an ultrasonic tank for 30 seconds. Spacers are sprayed ona first surface of the material. A cell is made using tow sheets of thematerial in such a way that a stretching direction of one sheet isorthogonal to the other. Polymerizable twisted nematic LC (TNLC)material is placed between the sheets. The cell is covered with amicropolarizer pattern mask. The horizontal rows are oriented 45° withrespect to the stretching direction of the original material. The celland mask are put into a pressing machine to make said cell and said maskclosed completely. Care is made to control a thickness of the cell. TheTNLC under the transparent area is polymerized with UV light into apermanent TN texture. The mask is removed. The cell is heated higherthan a nematic-isotropic transition temperature so that unpolymerized LCcovered by opaque strips of said mask experience a transition into anisotropic phase. UV light is used to polymerize uncured LC material atisotropic phase. Various materials are used as the covering material ofthe micropolarizers, including stretched PVA film, a linear polarizerand non-birefringent plastic film.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood with regard to the followingdescription, appended claims, and accompanying drawings where:

FIG. 1 illustrates a schematic of a PVA retarder based on μPoltechnology;

FIG. 2 illustrates optical rotation by a TN liquid crystal cell;

FIG. 3 illustrates the transmittance of PVA films and TN cell versuswavelength;

FIG. 4 illustrates a schematic of a TN based μPol;

FIG. 5 illustrates a TN based μPol made with the UV mask method;

FIG. 6 illustrates TN based μPol made with the E-field alignment method;

FIG. 7 illustrates a TN based μPol made with the multi-rubbing method;

FIG. 8 illustrates a TN μPol with 260 μm line width made by two-step UVexposure method;

FIG. 9 illustrates a TN μPol with 60 μm line width made byMultiple-Rubbing Method;

FIG. 10 illustrates a TN-μpol made using a flexible linear polarizingsheet as one substrate and a non-birefringent sheet as the othersubstrate;

FIG. 11 illustrates a TN-μpol fabricated directly on an LC display;

FIG. 12 illustrates a checkerboard TN-micropol aligned vertically andhorizontally;

FIG. 13 illustrates a TN-Micropol using two stretched PVA substratesinstead of glass using the two-step UV exposure method;

FIG. 14 illustrates a TN-Micropol using a linear polarizing sheet as onesubstrate and a Non-Birefringent sheet as the other substrate; and

FIG. 15 illustrates an improved TN-Micropol directly on a LCD display;and

FIG. 16 illustrates a 45-Degree micropol;

FIG. 17 illustrates a horizontally aligned TN-micropol;

FIG. 18 illustrates a vertically aligned TN-micropol for verticaldisplay pixel or sub-pixel columns.

DETAILED DESCRIPTION OF THE INVENTION

Principals of TN Liquid Crystal

When twisted nematic (TN) cells 200 satisfy the Mauguin condition, theincident linearly polarized light 202 can be considered to rotate withthe liquid crystal molecules. For a 90° TN cell, the Mauguin conditionis 2Δnd>>λ, in which d is the cell thickness; λ is wavelength ofincident light and Δn is birefringence, respectively. A TN film 204rotates the polarization axis of linear incident light by 90° 206, asshown in FIG. 2.

In a 90° TN cell, liquid crystal molecules are oriented in such a waythat the top layer is aligned in one direction while the bottom layer isperpendicularly aligned. The optical rotation by the TN cell exhibitsmuch less wavelength dependence than that of a λ/2 retarder. In otherwords, the bandwidth of a TN cell 300 is much wider than that of aretarder, as shown in FIG. 3. FIG. 3 shows the transmittance curves ofPVA 302 film and a TN cell 304 as a function of the wavelength, in whichthe transmittance measurement was taken by inserting the PVA film andthe TN cell between pairs of parallel polarizers. The thickness of TNcell is 10 μm and polymerizable liquid crystal CM428 is used and curedby UV light.

The TN film can be made relatively thin, typically, in the range of 5μ,as compared to 37.5μ of a commercial retarder from Polaroid. Such a thinlayer is most suitable for constructing a high-resolution μPol.Generally, liquid crystal materials used in display systems haveexcellent thermal as well as humidity resistance. Furthermore, if the TNcell is built with polymerizable (UV curable) liquid crystal, it can bepeeled off from the glass substrates and can be transferred to othersurfaces. TN μPol has the advantages of PVA μPol and overcomes theshortcomings of PVA Pol. The advantages of TN μPol are listed below:

Good spectral characteristics in the wide band;

-   -   Thin film thickness. By choosing large birefringence liquid        crystal material, TN μPol film can be very thin and exhibit the        wide bandwidth property.    -   Good spectral characteristics in the wide band;    -   High spatial resolution;    -   Small transition regions;    -   Easy to control line width;    -   Good thermal and humidity resistance;    -   Simple processing, low cost and high throughput.        TN Liquid Crystal Based μPol

If a TN film 400 is patterned to have alternatively spaced lines with402 and without 404 the optical rotation capability, a new μPol iscreated, as shown in FIG. 4. In the active strips in FIG. 4, liquidcrystal molecules are twisted so that they rotate the polarization angleof incident light. However, in the passive strips, molecules areun-twisted either in an isotropic phase or homogeneous or homeotropicphase so that they are unable to rotate the polarization.

TN uPol Processing

There are several ways to process a TN into a μPol. Four preliminarymethods have been proposed in the '871 application. They are:

-   -   Two-step UV exposure;    -   E-field (electric field) alignment;    -   Multiple-rubbing; and    -   Photo-induced alignment.

The following sections describe the fundamental details regarding thefour processing embodiments.

Two-step UV Exposure Method

This method uses a two-step UV exposure procedure to create a μPol thatconsists of nematic lines in a twisted and an isotropic state,respectively. The method involves the following procedure:

-   -   Coat polyimide on two glass plates;    -   Rub the polyimide coatings;    -   Make a cell with the two plates in such a way that the polyimide        rubbing direction of one plate is orthogonal to each other;    -   Fill in polymerizable nematic liquid crystal with light chiral        concentration so that a TN cell (film) is made;    -   Cover the TN cell with a mask which has an alternatively spaced        opaque and transparent strips;    -   Using a UV light to polymerize the nematic liquid crystals under        the transparent area into a permanent twisted texture;    -   Remove the mask;    -   Heat the cell higher than the nematic-isotropic transition        temperature so that those un-polymerized nematics covered by the        opaque mask strips experience a transition into the isotropic        phase, resulting in un-twisting of the liquid crystal molecules.        The twisting texture of the polymerized nematics remains        un-changed.    -   Finally, re-polymerize the previously uncured nematics into        isotropic phase. The resulting μPol will have the features as        shown in FIG. 5. This method can only be realized using the        polymerizable nematic liquid crystal.        E-Field (Electric Field) Alignment Method

In this method, an E-field is applied to a pre-patterned ITO electrodeto create a μPol that contains nematic lines in twisted and homeotropicstructure, respectively. The detailed procedures involve the followingprocedure:

-   -   Using photolithography methods, pattern one ITO glass plate to        have an alternatively spaced strips with and without ITO;    -   Coat polyimide on this patterned ITO glass and on another        un-patterned ITO glass plate;    -   Rub the polyimide in the proper directions;    -   Make a TN cell with the two glass plates with rubbing directions        perpendicular to each other;    -   Fill in nematic liquid crystal;    -   Apply an E-field to vertically align the nematic liquid crystal        under the stripped ITO electrodes. The nematic liquid crystal        under the strips without ITO remains in a TN texture.

The final texture of a μPol 600 constructed with this method isillustrated in FIG. 6.

Multiple-Rubbing Method

Patterned polyimide strips are created which have an orthogonal rubbingdirection so that liquid crystals below one strip are aligned into atwisted texture while the nematics under adjacent strips are alignedinto a homogeneous texture. A suitable polyimide must be used that thephotolithography process will not ruin. This method is outlined in thefollowing procedure.

-   -   Coat polyimide (SE 7311 from Brewer Scientific or other suitable        polyimide) on one glass substrate;    -   Unidirectionally rub the polyimide coating;    -   Coat photo resist (S 1815 from Microposit or other suitable        photo resist) on top of the rubbed polyimide;    -   Pattern the photo resist via photolithography to have        alternating spaced strips;    -   Re-rub the polyimide left un-covered by the photo resist strips        in a perpendicular direction to the first rubbing direction;    -   Remove all the photo resist by rinsing in an acetone bath;    -   Make a cell with the patterned glass plate and another        unidirectionally rubbed polyimide glass plate;    -   Fill the cell with nematic liquid crystal to form a μPol with        alternative strips in TN and homogenous texture.    -   If polymerizable liquid crystal is filled, cure the TN cell with        a suitable UV light.        The resulting μPol has the texture shown in FIG. 7.        Photo-induced Alignment Method

Recently a great deal of attention has been paid to the possibility toalign LC cells using photosensitive orientants. Because of itsnon-contact and easy to pattern properties, this method has someadvantages over rubbed polymer films. Some materials, such as polyvinyl4-methoxycinnamate (PVMC), polyvinylcinnamates (PVC), some polyimides,dyed polyimide, and azobenzene polymer, were found to have thecapability to align liquid crystal molecules after exposure under linearpolarization UV light. Liquid crystal molecules align in the directionperpendicular to the polarization direction of the UV light. There areseveral ways to realize a TN uPol by photo-induced alignment method thatare described in detail below.

A. Two-step Exposures with Linearly Polarized UV Light

For many of the photo-induced alignment materials mentioned above, whenexposed to linearly polarized UV light in different direction ofpolarization for two times, they have a property that lets liquidcrystal molecules align in the direction perpendicular to secondexposure direction. Therefore, this property provides a very easy way tomake TN uPol. The detail procedure given below:

-   -   Coat the suitable photo-induced alignment material (e.g.        polyimide) onto two glass plates;    -   Bake following the instructions of the coating manufacturer;    -   Expose both plates to linearly polarized UV light at 1500 to        2000 mj/sq cm.    -   With the mask placed over the plate, expose one of the plates        again under linearly polarized UV light with a polarization        direction perpendicular to the initial polarization direction at        1500 to 2000 mj/sq cm.    -   Fabricate the cell and fill with the nematic liquid crystal.        For those materials that liquid crystal cannot align properly        corresponding to a second exposure, a different procedure can be        followed:    -   Coat the suitable photo-induced alignment material onto a        two-glass plate bake.    -   Expose one plate to linearly polarized UV light at 1500 to 2000        mj/sq cm.    -   Expose another plate to linearly polarized UV light with the        mask placed over the plate, move the mask half period precisely        and then expose with linearly polarized (in a direction        perpendicular to the initial polarization direction) UV light        again.    -   Fabricate the cell and fill with the nematic liquid crystal.        B. Rubbing and Exposure with UV Linearly Polarized Light

In this method, rubbing processing and photo-induced alignment methodare combined to produce TN μPol. The following details the procedure:

-   -   Coat the proper photo-induced alignment material on two glass        plates followed by mechanical rubbing;    -   Pattern one of the glass substrate by shining it through a mask        with a light polarized in parallel to the rubbing direction;    -   Make a cell with such a patterned glass plate and another        uniformly rubbed polyimide plate;    -   Fill in twisted nematic material to form a μPol.        C. Bulk Alignment

In this method, the small amount of photoresist PVMC or azo dye isdirectly mixed into the nematic liquid crystal. When shined by alinearly polarized light, nematic molecules are perpendicularly alignedto the polarization direction. The following is the detailed procedure.

-   -   Coat polyimide onto two glass plates followed by rubbing;    -   Make a liquid crystal cell with the rubbed polyimide glass        plates;    -   Fill in nematics;    -   Shine the cell through a mask with a linear light polarized        perpendicularly to the rubbing direction to form a μPol.

The final texture of above μPol will be the same as shown in FIG. 7.Table I summarize the features of all the TN based uPol's made with thefour methods described above, respectively.

TABLE I Summary of the μPol's processed by the four methods RecommendedMethod Application Advantages Disadvantages Photo-mask Will fit mostSimple Relatively low applications processing resolution No ITO glassGood thermal stability Low cost E-field High-resolution High resolutionRelative applications. Good thermal complicated stability procedurePossible birefringence by those nematics in homeotropic state. Need ITOglass LC must have Δε ≠ 0. Multi-rubbing High-resolution Relative highRelatively applications. resolution complicated No ITO glass procedureGood thermal Possible stability birefringence by those nematics inhomogeneous state (ECB). Photo-induced High-resolution Simple Possiblealignment applications. processing birefringence by High resolutionthose nematics in No ITO homogeneous state Good thermal (ECB). stabilityDye must be outside the visible region.Pictures of TN uPol

Two TN uPol pictures are shown in FIGS. 8 and 9, which are observed witha crossed polarized microscope. FIG. 8 is a TN μPol 800 with 260 μm linewidth made by two-step UV exposure method. The white parts show TNtexture 802 while the dark parts 804 express the isotropic phase ofnematic. FIG. 9 is another TN μPol 900 with 60 um line width made bymultiple-rubbing method. Similarly, the white parts 902 show TNstructure but the dark parts 904 indicate homogenous alignment.

Using a Passive Linear Polarizer as the Substrate

The TN-micropol 1000 may also be constructed using a passive linearpolarizer 1002 as one substrate of the patterned TN-liquid crystal celland a non-birefringent layer 1004 as the second substrate as shown inthe FIG. 10. Potentially each of the four methods described above forfabricating a TN-micropol can be used for this method. The resulting TNcell would be a flexible layered film that could be applied to a LCDdisplay at the time of its manufacture. The process for construction ofsuch a TN-micropol structure would depend on which of the four methodsdescribed above is chosen. FIG. 10 illustrates this construction method.The peelable version of the TN micropol can also be realized using thisstructure if polymerizable TN liquid crystal is used in the fabrication.

The advantage of this method is that TN-micropol can be fabricated inlarge sheets or rolls and adhered to the LC display and the time of itsmanufacture. This structure replaces the normal analyzer (polarizer usedon the output of the display). Anti-glare measures can be used on thenon-birefringent substrate of this micropol structure to reduce glare asis done on a regular LC display.

Fabricating a TN-Micropol Directly on the LCD

An alternative to the previous method is fabrication of the TN-micropoldirectly on the LC display using the display itself as one substrate anda non-birefringent layer as the second substrate. As in the previousmethod, it is possible to use each of the fabrication methods (two-stepUV exposure method, e-field alignment method, multiple rubbing directionmethod, and photo induced alignment method) to make the TN-micropoldirectly on the display. The advantage of this method is that themicropol can be accurately fabricated on the display as an additionalstep in the LC display manufacturing process. FIG. 11 illustrates thisfabrication method.

TN-Micropol Fabrication Using Stretched PVA Substrates

The '871 TN-micropol patent application (parent of this application)also described the fabrication method (embodiment) called the “Two-stepUV Exposure Method” as described above. In this method, the TN-micropolis fabricated using polymerizable liquid crystal between two glasssubstrates. The basic process involves constructing and filling an LCcell using the polymerizable liquid crystal. The cell is then heated tothe clear point of the LC such that the LC transitions to the isotropicphase. A pattern mask is applied and UV light is used to cure theexposed LC. The cell is then cooled until the unexposed LC returns tothe twisted-nematic state and the mask is removed. After the coolingstep UV light is applied again to cure the previously unexposed LC.

The LC cell used in the processes described above is constructed usingtwo pieces of glass that are coated with polyimide and then rubbed tocause the LC molecules to align in the proper directions to achieve thetwisted nematic state at room temperatures. One glass substrate isrubbed in a first direction and the second glass substrate is rubbed ina perpendicular direction to the first substrate. This rubbing step canbe a source for errors that would reduce the yield in a manufacturingprocess.

The present embodiment replaces the glass substrates with stretched PVAsubstrates. The advantage of this design is that stretched PVA providesa sufficient surface for alignment of the LC molecules without rubbing.Therefore to fabricate a micropol using the method described above inwhich the glass is replaced by stretched PVA would require at least fourless processing steps (application of the polyimide substrate one,application of the polyimide to substrate two, buffing the firstsubstrate, and buffing the second substrate). FIG. 12 illustrates aschematic diagram of the micropol 1200 resulting from this process. Bothsubstrates 1202 and 1204 comprise stretched PVA with liquid crystalmaterial in a TN state 1204 and liquid crystal material in an isotropicstate 1206 in between the two substrates.

This embodiment outlines an alternative method for making TN μPol by thetwo-step UV exposure method by using stretched PVA film to replace ofthe glass substrate and other plastic film substrates as describedabove. The substrate is a stretched PVA film laminated on a birefringentplastic film. The liquid crystal can be aligned on the surface of thestretched PVA film, just like the LC aligned on the surface of rubbedpolyimide. The method involves the following steps as outline in TableII:

TABLE II Fabrication Steps for Dual PVA Substrate TN-Micropol 1. Cleanthe stretched PVA film (substrate) by 2-propanol in an ultrasonic tankfor 30 seconds; 2. Spray spacers on the surface of the film (the densityof the spaces is 50 to 200/sq. mm., each spacer having a diameter rangeof 5 to 20 μm). 3. Make a cell with the two sheets of the film in such away that the stretching direction of one sheet is orthogonal to theother, then fill in polymerizable twisted nematic LC (TNLC), or using aroller machine to laminate the LC between the two sheets; 4. Cover thecell with the micropol pattern mask. Ensure that the direction of thehorizontal rows is oriented 45° with respect to the stretching directionand rubbing directions; 5. Put the cell and the mask into pressingmachine that can make the cell and the mask closed completely andcontrol the cell thickness well; 6. Use UV light (2000-3000 mj. per sq.cm.) to polymerize the TNLC under the transparent area into a permanentTN texture; 7. Remove the mask; 8. Heat the cell higher than thenematic-isotropic transition temperature so that those unpolymerized LCcovered by opaque mask strips experience a transition into the isotropicphase; 9. Use UV light (2000-3000 mj. per sq. cm.) to polymerize theuncured LC at isotropic phase.

In addition to reducing the number of steps, using stretched PVAsubstrates affords the possibility of constructing micropols using acontinuous web process. The advantage of using a web process or a batchprocess is the potential for much lower cost per unit and higher volumeand yield. TN-micropol material can be stored and shipped in rolls toLCD manufacturers for application to their displays at their factories.

FIG. 12 shows a cross-sectional diagram of the dual PVA substratemicropol. In this case the glass substrates described above and in the'871 TN-micropol application are replaced by stretched PVA filmsubstrate. The advantage of using stretched PVA is that since LCmolecules readily line up along the stretching direction of the PVAfilm, there is no need for steps to coat the substrate with polyimideand to buff the polyimide in the direction of desired LC alignment. Thususing stretched PVA instead of glass reduces the number of process stepsfor fabrication.

The preferred method for fabrication the dual PVA substrate cell is thetwo-step UV exposure method described above and as described in theprevious TN-micropol application. However variations on themultiple-rubbing direction and photo-induced alignment methods may alsobe possible. The E-Field alignment method applies only for glasssubstrates with patterned ITO coatings and is therefore not applicablefor this micropol design. It is also preferable to use methods thatemploy polymerizable liquid crystal since the product contains noliquid, which precludes the possibility for leaks.

TN-Micropol Fabrication Using Passive Linear Polarizer Substrate

An alternate of the TN-micropol embodiment described above uses apassive linear polarizer as one substrate of the patterned TN-liquidcrystal cell as shown in FIG. 13. Using a linear polarizer as onesubstrate requires a modification to the process described in theprevious section but yields a micropol that is more readily usable tothe LCD industry. The process for fabricating a TN-micropol withstretched PVA and passive linear polarizers is outlined in Table IIIbelow.

TABLE III Fabrication Steps for PVA-Polarizer Substrate TN-Micropol 1.Clean the linear polarizer film with 2-propanol in an ultrasonic tankfor 30 seconds 2. Buff the linear polarizing film with a felt roller 3.Clean the stretched PVA film with 2-propanol in an ultrasonic tank for30 seconds 4. Spray spacers on the surface of the PVA film (spacerdiameter 5-20 μm) (spacer density 5-200/sq. mm. 5. Make a cell with theone sheets of the PVA film and one sheet of the polarizer film in such away that the stretching direction of the PVA sheet is orthogonal to therubbing direction of the polarizing film, then fill in polymerizabletwisted nematic LC (TNLC), or using a roller machine to laminate the LCbetween the two sheets; 6. Cover the cell with the micropol patternmask. Ensure the direction of the horizontal rows is oriented 45° withrespect to the stretching direction and rubbing directions; 7. Put thecell and the mask into pressing machine that can make the cell and themask closed completely and control the cell thickness well; 8. Using aUV light (2000-3000 mj/sq. cm.) to polymerize the TNLC under thetransparent area into a permanent TN texture; 9. Remove the mask; 10.Heat the cell higher then the nematic-isotropic transition temperatureso that those un-polymerized LC covered by opaque mask strips experiencea transition into the isotropic phase. 11. Finally using the UV(2000-3000 mj/sq. cm.) light to polymerize the uncured LC at isotropicphase.

The resulting TN cell is a flexible thin layered polarizing film thatcould be applied directly to an LC display at the time of itsmanufacture and replaces the polarizing film currently used by LCdisplay manufacturers. The process for construction of such aTN-micropol structure depends upon which of the four methods describedabove and in the '871 application is chosen.

As in the previous case an advantage of this method is that TN-micropolcan be fabricated in large sheets or rolls and adhered to the LC displayand the reduced time of its manufacture. This structure replaces thenormal analyzer (polarizer used on the output of the display).Anti-glare measures may be used on the PVA substrate of this micropolstructure to reduce glare as is done on a regular LC display.

FIG. 13 illustrates a cross-sectional diagram of the PVA-Polarizersubstrate TN-Micropol. The diagram is exactly the same as previouslydescribed except that a plastic linear polarizing sheet replaces thebottom PVA substrate. The exposed surface of the linear polarizer istypically a non-birefringent protective layer. In the two-step UVexposure method described above, this protective layer is buffed using afelt roller to provide a uniform alignment direction for the liquidcrystal molecules.

After the main portion of the micropol cell is fabricated (as shown inthe figure), an adhesive layer may be applied to the exposed side of thepolarizer film to help facilitate application to LCD displays.

TN-Micropol Fabrication Using Dual Non-Birefringent Plastic SheetSubstrate

The TN-micropol can be made by two-step UV exposure method by dualnon-birefringent plastic film to replace of the glass substrate. Theadvantage of this procedure is that can create large and continuousproduction line and TN micropol quality will be good because there is noany defect stripes in the isotropic phase come from materialbirefringent character or stretch character like PVA. It can laminatepolymerizable twisted nematic liquid crystal between two roll ofnon-birefringent plastic film, the film must be rubbed first and rubbingdirection is perpendicular each other. An additional more advantage isthat there is no coating procedure with polyimide, as compared withusing a glass substrate procedure. Then it can make TN-micropol bytwo-step UV exposure method as described above. The method involves theprocedure in Table IV.

TABLE IV Fabrication Steps for Dual Non-Birefringent Sheet SubstrateTN-Micropol 1. Clean the surface of non-birefringent plastic film. 2.Rubbing the surface of the films. 3. Spray spacers on the surface of thefilm. 4. Make a cell with two non-birefringent film which have rubbingdirection perpendicular each other. Then fill in or laminatepolymerizable twisted nematic LC between the two films. 5. Put themicropol pattern mask on the top of cell, Ensure the direction of thehorizontal rows is oriented 45° with respect to the rubbing direction.6. Put the cell and the mask into a pressing machine that can make thecell and mask closed completely and control the cell thickness well. 7.Using UV light to polymerize the TNLC under the transparent area into apermanent TN texture. 8. Remove the mask. 9. Heat the cell higher thanthe nematic-isotropic transition temperature so that thoseun-polymerized LC covered by opaque mask strips experience a transitioninto the isotropic phase. 10. Using UV light to polymerize the uncuredLC at isotropic phase. 11. Quality checking.Fabricating a TN-Micropol Directly on the LCD

As described above it may be advantageous to fabricate the PVA-Polarizersubstrate TN-micropol directly on the LC display using the polarizer ofthe LC display itself as one substrate and a PVA layer as the secondsubstrate. As in the previous method variation of the two-step UVexposure method is used to make the TN-micropol directly on the display.The advantage of this method is that the micropol can be accuratelyconstructed on the display as an additional step in the LC displaymanufacturing process.

FIG. 15 illustrates the concept of fabricating the PVA-substratemicropol directly on a LC display. The structure of the micropol itselfis identical to the PVA-polarizer substrate version previouslydescribed. The figure shows the structure of the micropol super-imposedover a cross-sectional view of an LCD display. The polarizer of thedisplay serves as the second substrate of the micropol, which isfabricated according to the method described above.

TN-Micropol Types

In addition to the processes used to make the TN-micropol there areseveral types of TN-micropols that are covered by this inventionincluding:

-   -   Two-Substrate type: In this case the micropol uses two glass        substrates and non-polymerizable LC material. The advantage is        that lower cost LC can be used.        -   Variation 1: both glass substrates are the same thickness        -   Variation 2: the glass substrate closest to the display is            made thinner to increase the viewing angle by reducing the            parallax effect.    -   Single-Substrate type: polymerizable LC material is used to so        that one substrate can be removed. Removing the substrate        increases the viewing angle by reducing the distance between the        TN-material and the active elements of the display.    -   Electrically switchable type: Using the E-field manufacturing        process the micropol can be constructed to switch between 2D and        3D. When no electric fields is applied, the entire micropol acts        as a singe LC cell causing all of the light from the display to        be rotated by 90°. When the electric field is applied, the LC        material between the patterned ITO electrodes enters the        homeotropic phase and therefore do not rotate the polarization        angle. A user can switch between 2D and 3D modes by activating a        switch that controls the electric field.        Variation of E-field Process

A variation of the E-field process would use polymerizable liquidcrystal to fabricate the micropol as follows:

-   -   Perform the previously described steps to make the cell.    -   Fill the cell with polymerizable LC material.    -   Apply the E-field to cause LC material between ITO electrodes to        enter the homeotropic phase.    -   Cure the polymerizable LC material using strong UV radiation.    -   Release the e-field.    -   Post processing and cleanup.        This method may be used to make the Single-Substrate type TN        micropol.        45-Degree TN Micropol

The existing application pertains to a 0°-90° TN-micropol in whichalternating lines rotate the polarization angle by either 0° or 90°.Another type of micropol can be constructed using all of the methodspresented above in which alternating lines rotate the polarization angleby either −45° or +45°. A representative drawing is shown in FIG. 15.Vertically polarized light enters from behind the micropol and isrotated to −45° or +45° depending on the row.

Finally it should be noted that the micropol lines could be orientedeither vertically or horizontally. When horizontal lines are used, themicropol is positioned to exactly line up over horizontal lines of thedisplay. When vertical lines are used, the micropol is positions suchthat it lines up exactly over the vertical columns of the display.Furthermore, the micropol line pitch may also be designed to coincidewith vertical columns of red, green, and blue pixel elements of thedisplay. Finally the TN micropol may be designed in a checkerboardpattern. These variations are shown in FIGS. 15 to 18.

The following additional references may be relevant to the disclosureand application and are hereby incorporated by reference. U.S. Pat. Nos.5,537,144 and 5,844,717 issued to Sadeg Faris. An article by S. M.Faris, in the SID 91 Digest, p. 840. An article by B. Bahadur, entitledLiquid Crystals Applications and Uses, published by World Scientific,1990, p232. A book by P. G. DE Gennes, entitled The Physics of LiquidCrystals, published by Clearendon Press Oxford, 1993. An article by T.Y. Marusii and Y. A. Reznikov in Mol. Mat., Vol. 3, p. 161, 1993. Anarticle by M. Schadt, H. Seiberle and A. Schuster, in Nature, Vol. 381,p. 212, 1996. An article by S. C. Jain and H. S. Kitzerrow, Appl. Phys.Lett. 64 (22), p. 2946, 1994. An article by W. M. Gibbons, P. J.Shannon, S. T. Sun and B. J. Swetlin, Nature, Vol 351, p. 49, 1991. Anarticle by G. P. Bryan-Brown and I. C. Sage, Liquid Crystals, Vol. 20,No. 6, p. 825, 1996. An article by K. Aoki, American Chemical Society,Vol. 8, p. 1014, 1992. An article by M. Schadt, H. Seiberle, A. Schusterand S. M. Kelly, Jpn. J. Appl. Phys., Vol. 34, p. L764, 1995.

While the invention has been described with reference to preferredembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition many modifications may be made to adapt a particular situationor material to the teachings of this invention without departing fromthe essential scope thereof. Therefore it is intended that the inventionnot be limited to the particular embodiments disclosed as the best modecontemplated for this invention, but that the invention will include allembodiments falling with the scope of the appended claims.

1. A method for creating a micropolarizer comprising: providing amaterial having a first and a second surface; cleaning material by2-propanol in an ultrasonic rank for 30 second; spraying spacers on afirst surface of said material; make a cell with a first and secondsheet of said material in such a way that a stretching direction of onesheet is orthogonal to the other; filling in polymerizable twistednematic LC (TNLC) between said sheets; covering said cell with amicropolarizer pattern mask; ensuring a direction of horizontal rows isoriented 45° with respect to said stretching direction; placing saidcell and said mask into a pressing machine to make said cell and saidmask closed completely; controlling a thickness of said cell;polymerizing the TNLC under the transparent area with UV light into apermanent TN texture; removing said mask; heating the cell higher than anematic-isotropic transition temperature so that unpolymerized LCcovered by opaque strips of said mask experience a transition into anisotropic phase; using UV light to polymerize uncured LC material atisotropic phase.
 2. The method of claim 1, wherein said mask hasalternate transparent and opaque strips covering said cell or filmwhereby a solidifying energy is being selectively applied there through;and partially solidifying some portions said liquid crystal.
 3. Themethod of claim 1 wherein a density of said spaces is 50 to 200 sq. mm.4. The method of claim 1 wherein said spacers have a diameter range of 5to 20 μm.
 5. The method of claim 1 comprising using a roller machine tolaminate said LC between said two sheets as an alternative to filling insaid polymerizable twisted nematic.
 6. The method of claim 1, wherein:said two plates comprising stretched PVA film.
 7. The method of claim 1,wherein said liquid crystal comprises a nematic liquid crystal.
 8. Themethod of claim 1, wherein said liquid crystal comprises a nematicliquid crystal.
 9. The method of claim 8, wherein said nematic liquidcrystal comprises a type of polymerizable nematic liquid crystal. 10.The method of claim 8, wherein said nematic liquid crystal comprises acomprises a type of polymerizable nematic liquid crystal.
 11. A methodfor creating a micropolarizer, comprising: providing anon-birefringement plastic film; cleaning said film with 2-propanolwithin an ultrasonic tank; rubbing a first surface of saidnon-birefringent film, spraying spacers on a first surface of said PVAfilm; making a cell with said two sheets of said non-birefringent filmin such a way that a rubbing direction of a first non-birefringent filmis orthogonal to a rubbing direction of a second birefringent film;filling in or laminating polymerizable twisted nematic LC (TNLC)material between said first and second sheets of non-birefringent film;covering said cell with a micropolarizer pattern mask; ensuring adirection of horizontal rows is oriented 45° with respect to saidrubbing directions; placing said cell and said mask into a pressingmachine to make said cell and said mask closed completely; controlling athickness of said cell; polymerizing the TNLC material under atransparent area of said mask with UV light into a permanent TN texture;removing said mask; heating the cell higher than a nematic-isotropictransition temperature so that unpolymerized LC covered by opaque stripsof said mask experience a transition into a isotropic phase; and usingUV light to polymerize uncured LC material at isotropic phase.
 12. Themethod of claim 11, wherein said mask has alternate transparent andopaque strips covering said cell or film whereby a solidifying energy isbeing selectively applied there through; and partially solidifying someportions said liquid crystal.
 13. The method of claim 11 wherein adensity of said spaces is 50 to 200 sq. mm.
 14. The method of claim 11wherein said spacers have a diameter range of 5 to 20 μm.
 15. The methodof claim 11 comprising using a roller machine to laminate said LCbetween said two sheets as an alternative to filling in saidpolymerizable twisted nematic.
 16. A liquid crystal display device,comprising: an input surface for receiving incident light; an outputsurface for emanating a processed light; and a micropolarizer based ontwisted nematic liquid crystals produced by a method comprising a liquidcrystal display device produced by the method described substantially byany of claim 1-9 or
 10. 17. A liquid crystal display device, comprising:an input surface for receiving incident light; an output surface foremanating a processed light; and a micropolarizer based on twistednematic liquid crystals produced by a method comprising a liquid crystaldisplay device produced by the method described substantially by any ofclaims 11-15.